Abstract
Direct numerical simulation has been performed to study a polymer drag-reducing channel flow by using a discrete-element model. And then, wavelet analyses are employed to investigate the multiresolution characteristics of velocity components based on DNS data. Wavelet decomposition is applied to decompose velocity fluctuation time series into ten different frequency components including approximate component and detailed components, which show more regular intermittency and burst events in drag-reducing flow. The energy contribution, intermittent factor, and intermittent energy are calculated to investigate characteristics of different frequency components. The results indicate that energy contributions of different frequency components are redistributed by polymer additives. The energy contribution of streamwise approximate component in drag-reducing flow is up to 82%, much more than 25% in the Newtonian flow. Feature of turbulent multiscale structures is shown intuitively by continuous wavelet transform, verifying that turbulent structures become much more regular in drag-reducing flow.
Highlights
It is well known that the addition of a small amount of polymer solution into liquid such as water at high Reynolds number can suppress turbulence and significantly reduce turbulent friction drag
Dimitropoulos et al [6] predicted drag reduction for a variety of rheological parameters in the FENE-P and the Giesekus models, and verified the hypothesis that one of the prerequisites for the phenomenon of drag reduction is sufficiently enhanced extensional viscosity, corresponding to the level of intensity and duration of extensional rates typically encountered during the turbulent flow
Housiadas et al [12] examined the efforts of changes in the flow viscoelasticity and the friction Reynolds number on several higher order statistics and on coherent structures of turbulence
Summary
It is well known that the addition of a small amount of polymer solution into liquid such as water at high Reynolds number can suppress turbulence and significantly reduce turbulent friction drag. To make a further study on mechanism of drag reduction, multiresolution analysis method should be applied to investigate the energy distribution and turbulent structures of different time scales in drag-reducing flow. The instantaneous information of polymer drag-reducing flow is provided by direct numerical simulation with the discrete-element model. Based on these DNS data, multiresolution structures of drag-reducing flow are analyzed by wavelet transformation and wavelet decomposition in time domain. Multiscale flow structures of Newtonian flow and dragreducing flow are shown by continuous wavelet transform, respectively
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
